Professor Yuzhuo Li and
his group are doing research that involves liposomes. The study of liposomes
is very important due their similarity to biological membranes and their
therapeutic value as delivery agents for enzymes, drugs, genetic manipulation,
and diagnostic imaging. The behavior of a liposome as a biological agent
is dependent upon the size, as well as other physical characteristics,
including composition, surface properties, lamellarity, and diffusion
rates for small molecules. For example, polymers attached to the surface
of a liposome (Stealth Liposome) can significantly alter its lifetime
in a biological system. Working with Dr. Greg Slack at DuPont Pharmaceuticals,
Professor Li and his graduate student Nicole Heldt and undergraduate student
Michele Gauger have investigated a range of issues related to the characterization
and preparation of polymer stabilized lipsome systems. They have examined
the effect on the size of the vesicles by quantitative addition of a hydrotrope
and a polymer to a vesicle-forming system. They have also investigated
the usefulness of a range of analytical techniques in the characterization
and comparison of conventional and stealth liposome systems including
NMR, TEM, Fluorescence, and dynamic light scattering. The goal of this
research is to develop an optimized liposome system for drug delivery
and medical diagnostic applications.

Professor Gary Ga-Er Yu
has been working on the preparation and solution properties of amphiphilic
block copolymers, including AB type diblock copolymers: PEO-b-PPO, PEO-b-PBO,
PAA-b-PS, PAA-PMMA, ABA type triblock copolymers: PEO-PPO-PEO, PEO-PBO-PEO,
etc.. Recently, he and his group have experimentally proved that uniform
amphiphilic diblock and triblock copolymers with the same composition
and the same hydrophilic block length or AmBn and AmB2nAm form micelles
in aqueous solutions with the same hydrodynamic radii. Now he is developing
ABC type amphiphilic block copolymer systems for better solubilization
properties, e.g., for drug delivery purposes or solubilization of organic
compounds in the micelles. Biodegradable and biocompatible polymers and
copolymers are the topics he has been actively involved in.. Professor
Yu has developed methods for obtaining low molecular weight poly(3-hydroxyalkanoate)s
(PHA) from bacterial PHA and the preparation of amphiphilic block copolymers
with PEO (collaborating with Professor R.H. Marchessault at McGill University).

Block Copolymer
Production

Professor Devon Shipp's
research, conducted in association with workers at Carnegie Mellon University,
led to several breakthroughs in polymer synthesis, especially the production
of block copolymers via living radical polymerization. This research has
resulted in the first report of using atom transfer radical polymerization
(ATRP) to synthesize water-borne block copolymers. These block copolymers
had well-defined molecular weights and molecular weight distributions.
Other work has also produced all-acrylic thermoplastic elastomers, based
on methyl methacrylate and n-butyl acrylate. This was achieved using a
one-pot ATRP procedure that allows for easy synthesis and used readily
available starting materials. Physical characterization of the all-acrylic
polymers showed they exhibit typical thermoplastic elastomer behavior,
and thus could become an alternative to styrene-diene analogues. They
may also offer several advantages like superior processability and better
resistance to solvent and thermal degradation. Kinetic modeling has been
successful in showing the importance of the persistent radical effect
in ATRP, as well as the significance of chain length dependent termination
rate coefficients. The model developed for ATRP allows one to predict
various outcomes of the polymerization, including molecular weight, reaction
rates and polymer chain functionality. Professor Shipp's current work
is focused on further ATRP studies, and on developing another living radical
polymerization method - nitroxide-mediated polymerization (NMP). He plans
to use NMP for the production of polymer-silicate (clay) nanocomposites,
and to expand NMP so as to allow polymerization to be photo-initiated.

NANOPARTICLE
/ POLYMER COMPOSITES

Professor Raymond Mackay
and graduate student Florentina Pavel have used w/o microemulsions stabilized
by a polymerizable surfactant to produce polymethacrylate nanolatexes
on the order of 5-10 nanometers in diameter. Recently, these studies have
been extended to systems in which the oil itself is a polymerizable monomer.
Nanoparticles have been synthesized in-situ in the liquid microemulsions,
which are subsequently polymerized to form transparent polymer-nanoparticle
composites. Studies are underway to explore the range of composition to
which this process can be applied. Some of these results were recently
reported at the International Conference on surface and Interface Science
at the University of Bristo